GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Body and Accessories 🢒 Stationary Windows 🢒 DTC 034

Circuit Description

The HVAC control module uses the supply voltage of the heated mirrors as an input. With the rear window defogger enabled, the battery positive voltage will be present on the supply voltage circuit of the heated mirrors. The HVAC control module tests the supply voltage circuit of the heated mirrors every 150 milliseconds.

Conditions for Running the DTC
    • The engine is running.
    • The rear window defogger is enabled.

Conditions for Setting the DTC

One of the following conditions can cause this DTC to set:

    • An open in the ignition 1 voltage circuit of the heated outside rearview mirror and rear window defogger relay coil.
    • An open or short to ground in the battery positive voltage circuit of the heated outside rearview mirror and rear window defogger relay switch.
    • An open or short to ground in the supply voltage circuit of the HTD MIRROR fuse.
    • An open or short to ground in the supply voltage circuit of the heated mirrors.

Action Taken When the DTC Sets

The rear window defogger is disabled.

Conditions for Clearing the DTC

A history DTC will clear after 20 consecutive ignition cycles.

The DTC will clear from current status when one of the following conditions is no longer detected:

    • An open in the ignition 1 voltage circuit of the heated outside rearview mirror and rear window defogger relay coil.
    • An open or short to ground in the battery positive voltage circuit of the heated outside rearview mirror and rear window defogger relay switch.
    • An open or short to ground in the supply voltage circuit of the HTD MIRROR fuse.
    • An open or short to ground in the supply voltage circuit of the heated mirrors.

Step

Action

Yes

No

Schematic Reference: Defogger Schematics

1

Did you perform the Stationary Windows Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Stationary Windows

2
  1. Start the engine.
  2. Depress the rear window defogger switch.
  3. Observe the rear window defogger indicator on the HVAC Control Module.

Does the rear window defogger indicator illuminate?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the HTD MIRROR fuse.
  3. Connect a test lamp between the supply voltage circuit of the HTD MIRROR fuse and a good ground.
  4. Start the engine.
  5. Depress the rear window defogger switch.

Does the test lamp illuminate?

Go to Step 6

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the Heated Outside Rearview Mirror and Rear Window Defogger relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the Ignition 1 voltage circuit of the Heated Outside Rearview Mirror and Rear Window Defogger relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 12

5

Connect a test lamp between the battery positive voltage circuit of the Heated Outside Rearview Mirror and Rear Window Defogger relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 8

6

Test the supply voltage circuit of the heated mirrors for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 10

7

Test the supply voltage circuit of the HTD MIRROR fuse for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 11

8

Test the battery positive voltage circuit of the Heated Outside Rearview Mirror and Rear Window Defogger relay switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 9

9

Test the supply voltage circuit of the rear window defogger for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 13

10

Inspect for a poor connection at the harness connector of the HVAC Control Module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 14

11

Inspect for a poor connection at the Heated Outside Rearview Mirror and Rear Window Defogger relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 15

12

Repair an open or short to ground in the Ignition 1 voltage circuit of the Heated Outside Rearview Mirror and Rear Window Defogger relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

--

13

Repair a short to ground in the supply voltage circuit of the HTD MIRROR fuse. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

--

14

Replace the HVAC Control Module. Refer to HVAC Control Module Replacement in HVAC Systems - Automatic.

Did you complete the replacement?

Go to Step 16

--

15

Replace the Heated Outside Rearview Mirror and Rear Window Defogger relay.

Did you complete the replacement?

Go to Step 16

--

16
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK